TDDFT Studies of Electronic Structure and First Hyperpolarizability of Tetra-nuclear Cubane-like Transition Metal Clusters

A series of tri-nuclear transition metal clusters with incomplete cubane-like configurations have been studied by TDDFT method. The calculations show that they have enormously large second-order polarizabilities () and are potential nonlinear optical materials for infrared double frequency conversion1. In this paper some tetra-nuclear transition metal clusters with cubane-like configurations, MCu3X4 (PPh3)3 (M=W, Mo; X= S, O, Cl, Se, Br), were studied by TDDFT method for a reference…     

双圈图的零度与其匹配数之间的关系

Let G be a graph with n(G) vertices and m(G) be its matching number.The nullity of G,denoted by η(G),is the multiplicity of the eigenvalue zero of adjacency matrix of G.It is well known that if G is a tree,then η(G) = n(G)-2m(G).Guo et al.[Jiming GUO,Weigen YAN,Yeongnan YEH.On the nullity and the matching number of unicyclic graphs.Linear Alg.Appl.,2009,431:1293 1301]proved that if G is a unicyclic graph,then η(G)equals n(G)-2m(G)-1,n(G)-2m(G),or n(G)-2m(G) +2.In this paper,we prove that if G is a bicyclic graph,then η(G) equals n(G)-2m(G),n(G)-2m(G)±1,n(G)-2m(G)±2or n(G)-2m(G) + 4.We also give a characterization of these six types of bicyclic graphs corresponding to each nullity.     

A phenomenological theory for polarization flop in spiral multiferroic TbMnO<Subscript>3</Subscript>

A phenomenological Landau theory has been used to explain magnetic field-driven polarization flop in TbMnO ₃. The Néel wall-like magnetic structure in spiral multiferroics induces a space-dependent internal magnetic field which exerts a torque on spins to rotate bc-spiral to ab-spiral. The external magnetic field is argued to be competing with easy axis anisotropy and the system stabilizes when anisotropy is minimum. With the help of Landau free energy with DM magnetoelectric coupling and a general ansatz for magnetization, the phenomenon of polarization flop has been explained. Relation between T_flop and critical magnetic field has been established and found to be in good agreement with the experiment. This could be an indication that anisotropy of the system is temperature- and magnetic field-dependent.     

Homo and hetero glaser coupling involving acetylene derivatives of trifluoromethanesulfonamide

Glaser homocoupling of N,N-bispropargyltriflamide led to the formation of N,N'-hexa-2,4-diyne-1,6-diylbis(N-prop-2-yne-1-triflamide). Further condensation into a 14-membered heterocycle, 1,8-bis-(triflyl)-1,8-diazacyclotetradeca-3,5,10,12-tetrayne did not occur evidently because of rigid steric requirements to the cyclization. In the Glaser heterocoupling of N-propargyltriflamide with arylacetylenes ArC≡CH (Ar = Ph, p-CNC₆H₄) the condensation products formed in 20–30% yields.     

Immobilized organometallic catalysts in the catalytic polymerization of olefins

Studies in the field of supported Ziegler-Natta catalysts employed for the polymerization of olefins that were begun by works performed under the guidance of Prof. Chirkov are reviewed in brief. The development of immobilization procedure for metallocene catalysts including the synthesis of alkylaluminoxanes heterogenized on the support surface via the partial hydrolysis of AlR₃ by water contained in the support and subsequent supporting of a metallocene is described. It is revealed how the immobilization of various metallocenes on the solid surface affects the activity of the catalysts and the structure and molecular mass of the polymers. The use of immobilized organometallic catalysts for the polymerization filling of polyolefin matrices aimed at the design of new polymer composites with special characteristics and preparation of polyolefin nanocomposites is considered.     

Green synthesis of methyl trifluoropyruvate catalyzed by solid acids

Solid acids – NiSO₄/Al₂O₃, Fe₂(SO₄)₃/Al₂O₃ and TiO₂/SO₄²⁻ – appeared to be effective catalysts for the acid catalyzed synthesis of methyl ester of trifluoropyruvic acid. They are active at 150–180 °C.     

A study of sorption and decomposition of ozone on microfibrous filtering materials

Decomposition of ozone on commercial and pilot filtering microfibrous materials based on polymers, glass fibers, and carbonized polymeric fibers was studied. Original Russian Text A.I. Klimuk, L.A. Obvintseva, A.D. Shepelev, V.L. Kuchaev, M.P. Dmitrieva, E.N. Ushakova, A.K. Avetisov, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81, No. 4, pp. 593–597.     

Determination of diffusion coefficients for sulfide ions in solid electrolytes on the basis of BaSm<Subscript>2</Subscript>S<Subscript>4</Subscript> and CaGd<Subscript>2</Subscript>S<Subscript>4</Subscript>

Coefficients of self-diffusion and coefficients of diffusion of the sulfur ion in solid electrolytes BaSm₂S₄ and CaGd₂S₄ are determined with recourse to methods of conductimetry and potentiostatic chronoamperometry. A vacancy mechanism for the defect formation in solid solutions on the basis of barium thiosamarate and calcium thiogadolynate is proposed.     

Electrochemical Methods for Studying Transport Properties and the Type of Ionic Conduction in Solid Electrolytes Based on CaPr<Subscript>2</Subscript>S<Subscript>4</Subscript> and Ca(Ba)Sm<Subscript>2</Subscript>S<Subscript>4</Subscript>

The theoretical feasibility of sulfide ion transport in phases based on MeLn₂S₄ (Me = Ca, Ba; Ln = Sm, Pr) is considered. Regions of solid solutions on the basis of ternary compounds are determined. A systematic investigation of phases is performed with the application of a variety of electrochemical methods, specifically, the conductimetry, emf in chemical concentration cells with and without transport, and Tubandt methods.__________Translated from Elektrokhimiya, Vol. 41, No. 6, 2005, pp. 707–713.Original Russian Text Copyright © 2005 by Ushakova, Kalinina, Fominykh, Yurlov, Murin.Published on the basis of a report delivered at the VII Meeting on Fundamental Problems in Solid-State Ionics (Chernogolovka-2004).     

尿素分子团簇线性和一阶非线性光学极化率的理论计算

检验分子晶体非线性光学极化率的可加性,对于确认有向气体模型(Oriented-Gas Model) 具有重要的科学意义,对探索新型实用的分子非线性光学材料也有实际的意义。本文对尿素晶体中分子簇非线性光学极化率的可加性做了详尽的理论研究。首次做到了尿素分子最近邻排布团簇的非线性光学极化率的从头算,从而扩展了前人的工作。研究结果有效地确认了有向气体模型。同时,我们还提出了壳层结构模型 (Shell-Structure Model),用以解决有向气体模型中的缺陷,可实现更为有效可靠地计算晶体宏观非线性光学系数。